Due to environmental concerns, governmental entities have steadily imposed stricter regulations on the amount and type of exhaust emitted by vehicles powered by the internal combustion engine. Moreover, the amount of noise produced by such engines must also meet stringent standards. The federal and state regulations may improve air quality and decrease noise pollution, however these mandates also produce severe drawbacks because the exhaust emission and sound control devices increase fuel consumption and decrease power production by the affected engines. The exhaust emission and sound control devices hamper engine performance as a result of back pressure of exhaust gas created by the very equipment that muffles the noise and cleans the exhaust gas. Designs of exhaust emission and sound control devices that increase exhaust flow-through will mitigate back pressure on the engine, thereby improving overall engine performance while still meeting demanding governmental environmental standards.
A number of systems have been proposed to provide a more efficient means of reducing noise and/or air pollution from internal combustion engine exhaust. Examples of such proposed systems are found in U.S. patents issued to Kojima (U.S. Pat. No. 4,533,015), Michikawa (U.S. Pat. No. 4,339,918), Taniguchi (U.S. Pat. No. 4,331,213), Harris et al. (U.S. Pat. No. 4,317,502), Taniguchi (U.S. Pat. No. 4,303,143), Kasper (U.S. Pat. No. 4,222,456), Everett (U.S. Pat. No. 4,129,196), Lyman (U.S. Pat. No. (4,109,753), Kashiwara et al (U.S. Pat. No. 4,050,539), and Iapella et al (U.S. Pat. No. 3,016,692), amongst others. However, none of these prior art references facilitate an improvement in engine power output or fuel efficiency. The quest to decrease noise and exhaust emissions, while off-setting the concomitant degradation of engine performance manifested by decreases in fuel efficiency, horsepower, and torque production, proves to be an ongoing struggle.
In particular the system proposed by Lyman (U.S. Pat. No. 4,109,753) presents a muffler assembly for substantially dampening acoustical vibrations of engine exhaust gases. The muffler assembly includes a flow control means, such as a diffuser having a centrally disposed baffle with radially extending deflector vanes and axially extending tabs. The diffuser is positioned near the inlet to an apertured louver tube within a loosely compact shell of sound attenuating material. The apertured louver tube has approximately the same cross sectional area as the inlet and outlet tubes. The diffuser has a planer baffle that substantially blocks and restricts the axial flow of exhaust gases along portions of the longitudinal axis of the louver tube, deflects the flow of exhaust gases toward the sound attenuating material and creates a turbulent flow. However, the Lyman muffler assembly fails to improve engine performance (i.e. fuel efficiency, horsepower, torque), and differs from the present invention in terms of blade (sharp versus rounded) and baffle geometry (planer versus cone shaped), expansion chamber cross sectional area (inlet area same as louver tube versus expansion chamber with larger cross section), and exhaust gas flows (turbulent versus contoured) as will be described.